Box-shaped structure for work machine

ABSTRACT

A boom includes a body and a base end bracket. The body includes a straight section and a wide section. When viewed from above, a width of the straight section is substantially constant. When viewed from above, a width of the wide section increases toward the base end bracket. The straight section and the wide section are smoothly continuous to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National stage application of International Application No. PCT/JP2017/035316, filed on Sep. 28, 2017. This U.S. National stage application claims priority under 35 U.S.C. § 119(a) to Japanese Patent Application No. 2016-193969, filed in Japan on Sep. 30, 2016, the entire contents of which are hereby incorporated herein by reference.

BACKGROUND

The present invention relates to a box-shaped structure for a work machine.

A work vehicle, such as a hydraulic excavator, includes a work machine that has a box-shaped structure formed of, for example, a boom and an arm. In Japanese Unexamined Patent application publication No. H6-220880, there is proposed a method of forming a box-shaped structure with two separate bodies welded together along a neutral axis, and expanding the width of the box-shaped structure at an end portion thereof. The method disclosed in Japanese Unexamined Patent application publication No. H6-220880 describes that it can reduce a cross-section of the box-shaped structure along a longitudinal direction thereof to provide a lighter structure, while also preventing a decrease in strength of the end portion that is mounted to another structure.

SUMMARY

In the box-shaped structure of Japanese Unexamined Patent application publication No. H6-220880A, each side plate of the box-shaped structure is bent at a plurality of positions in order to increase the width at an end portion thereof. Because of this, stress concentrates at the bent portions of each side plate. In particular, in the box-shaped structure of Japanese Unexamined Patent application publication No. H6-220880 that has been made with a smaller cross-section, more stress is generated at the bent portions of each side plate due to the bending of the box-shaped structure.

The present invention has been made in light of the above-described problem, and it is an object of the present invention to provide a box-shaped structure for a work machine that can have improved durability.

A box-shaped structure for a work machine according to a first aspect of the present invention includes a body that extends in a longitudinal direction and a bracket that is connected to one end of the body. The body including a straight section having a substantially constant width when viewed from above, and a wide section that is connected to the bracket and has a width that increases toward the bracket when viewed from above, and the straight section and the wide section are smoothly continuous to each other.

According to the box-shaped structure for a work machine according to the first aspect of the present invention, the wide section has a width that increases toward the bracket, and hence the cross-sectional area of the body can be increased on the bracket side. With this configuration, strength of the body can be enhanced. In addition, because the straight section and the wide section are smoothly continuous to each other, it is possible to reduce locally concentrating stresses in the body.

A box-shaped structure for a work machine according to a second aspect of the present invention is the box-shaped structure for a work machine according to the first aspect, in which the body is formed of a top plate, a bottom plate, a first side plate and a second side plate. The bracket includes a first abutment surface that abuts against the first side plate and a second abutment surface that abuts against the second side plate, and each of the first abutment surface and the second abutment surface are angled with respect to the longitudinal direction of the body.

A box-shaped structure for a work machine according to a third aspect of the present invention is the box-shaped structure for a work machine according to the first or second aspect, in which the body has a center boss centrally located in the longitudinal direction, and the bracket has an end boss. The straight section is smoothly continuous to the wide section at a predetermined position between the center boss and the end boss. A ratio of a first interval between a center axis of the center boss and the predetermined position to a second interval between a center axis of the end boss and the predetermined position is from 1:1 to 4:1.

A method of manufacturing a box-shaped structure for a work machine according to a fourth aspect of the present invention including the steps of: placing a first side plate and a second side plate on a bottom plate; pushing one end portion of the first side plate and one end portion of the second side plate outward using a lining; sandwiching and fixing a bracket between the end portions of the first side plate and the second side plate; and fixing a top plate on the first side plate and the second side plate.

According to the present invention, there can be provided a box-shaped structure for a work machine that can have improved durability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a hydraulic excavator.

FIG. 2 is a side view of a boom of the hydraulic excavator of FIG. 1.

FIG. 3 is a plan view of the boom of FIG. 2.

FIG. 4 is a cross-sectional view taken along the line A-A of the boom in FIG. 2.

FIG. 5 is a partially expanded view of the boom of FIG. 4.

FIGS. 6A-6D are schematic diagrams illustrating a method of manufacturing the boom.

FIG. 7 is a schematic diagram illustrating the method of manufacturing the boom including a pressing tool and a lining tool.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Configuration of Hydraulic Excavator 1

FIG. 1 is a side view for illustrating a hydraulic excavator 1. Herein, “up,” “down,” “front,” “rear,” “left” and “right” are directions from the point of view of an operator sitting in a driver's seat.

The hydraulic excavator 1 includes a traveling body 10, a turning body 11, a counterweight 12, an engine compartment 13, a device compartment 14, a cab 15 and a work machine 16.

The traveling body 10 has a pair of track pads that are rotatable independently of each other. The turning body 11 is turnably disposed on the traveling body 10. The turning body 11 provides a vehicle body frame of the hydraulic excavator 1.

The counterweight 12 is disposed on a rear end portion of the turning body 11. The engine compartment 13 is disposed on the turning body 11. The engine compartment 13 is disposed on the turning body 11 in front of the counterweight 12. The engine compartment 13 houses an engine, an exhaust gas processing device and other components. The device compartment 14 is disposed on the turning body 11 in front of the engine compartment 13. The device compartment 14 houses a hydraulic pump, a fuel tank, a working fluid tank and other components. The cab 15 is disposed on the turning body 11 in front of the device compartment 14. The cab 15 is provided with a driver's seat where an operator sits.

The work machine 16 is mounted in a vertically swingable manner on the turning body 11 in front of the device compartment 14 and to the right of the cab 15. The work machine 16 includes a boom 17, an arm 18, a bucket 19, a pair of boom cylinders 20, an arm cylinder 21 and a bucket cylinder 22. The boom 17 is an example of the “box-shaped structure for a work machine.”

A base end portion of the boom 17 is swingably mounted to the turning body 11. A tip end portion of the boom 17 is swingably mounted to a base end side bracket 18 b. A base end portion of the arm 18 is mounted to the base end side bracket 18 b. The bucket 19 is swingably mounted to a bucket bracket 18 a that is provided on a tip end portion of the arm 18.

Both boom cylinders 20 drive the boom 17. The boom cylinders 20 are linked to the turning body 11 and a center boss CB of the boom 17. The arm cylinder 21 drives the arm 18. The bucket cylinder 22 drives the bucket 19.

Configuration of Boom 17

A configuration of the boom 17 according to this embodiment is described with reference to the figures. FIG. 2 is a side view for illustrating the boom 17. FIG. 3 is a plan view for illustrating the boom 17.

The boom 17 includes a body 30, a base end bracket 31 and an arm bracket 32. The base end bracket 31 is an example of a “bracket” in this embodiment.

The body 30 extends in a longitudinal direction. The body 30 has a boomerang-like shape when viewed from the side. The body 30 is a hollow tube. The body 30 forms a box shape with a top plate 33, a bottom plate 34, a first side plate 35 and a second side plate 36.

The first side plate 35 and the second side plate 36 are disposed with a predetermined clearance therebetween. A rear end portion of the first side plate 35 is deformed so as to expand outward. Similarly, a rear end portion of the second side plate 36 is deformed so as to expand outward. A center boss CB that extends in a width direction is attached to the first side plate 35 and the second side plate 36. The center boss CB is located substantially at the center of the body 30.

The top plate 33 is disposed so as to cover a top opening of a space formed between the first side plate 35 and the second side plate 36. The bottom plate 34 is disposed so as to cover a bottom opening of the space formed between the first side plate 35 and the second side plate 36.

The base end bracket 31 is connected to a rear end of the body 30. The base end bracket 31 is provided with an end boss EB that extends in the width direction. The base end bracket 31 may be an ingot that is formed by casting a metal material.

The arm bracket 32 is connected to a front end of the body 30. The arm bracket 32 is provided with an arm mounting hole 32 a. The arm 18 (see FIG. 1) is mounted in the arm mounting hole 32 a. The arm bracket 32 may be an ingot that is formed by casting a metal material.

Configuration of Body 30

A configuration of the body 30 is described with reference to FIGS. 2 and 3.

The body 30 includes a straight section 30 a and a wide section 30 b. The straight section 30 a is formed of front side portions of each of the top plate 33, the bottom plate 34, the first side plate 35 and the second side plate 36. The wide section 30 b is formed of rear side portions of each of the top plate 33, the bottom plate 34, the first side plate 35 and the second side plate 36.

The straight section 30 a is continuous to the wide section 30 b at a predetermined position LP between the center boss CB and the end boss EB. The straight section 30 a is smoothly continuous to the wide section 30 b at the predetermined position LP. In this embodiment, “smoothly continuous” means that there is no point of inflection in any of the top plate 33, the bottom plate 34, the first side plate 35 and the second side plate 36 at the predetermined position LP. None of the top plate 33, the bottom plate 34, the first side plate 35 and the second side plate 36 are bent at the predetermined position LP. Therefore, a drastic change in the cross-sectional area of the body 30 at the predetermined position LP is eliminated.

In this embodiment, as illustrated in FIG. 2, the predetermined position LP at which the straight section 30 a is smoothly continuous to the wide section 30 b is located substantially center between the center boss CB and the end boss EB. On an imaginary line that connects the center boss CB and the end boss EB to each other, an interval L1 between a center axis AX1 of the center boss CB and the predetermined position LP is substantially equal to an interval L2 between a center axis AX2 of the end boss EB and the predetermined position LP. In this embodiment, a ratio of the interval L1 to the interval L2 is approximately 1:1. However, the predetermined position LP may be anywhere as long as the wide section 30 b does not interfere with the pair of boom cylinders 20 (see FIG. 1). For example, the ratio of the interval L1 to the interval L2 can be set between 1:1 to 4:1.

The straight section 30 a is connected to the front of the wide section 30 b. As illustrated in FIG. 3, when viewed from above, the straight section 30 a has a width Wa of that is substantially constant in the longitudinal direction. In this embodiment, the width Wa of the straight section 30 a is 450 mm.

The wide section 30 b is connected to the rear of the straight section 30 a. As illustrated in FIG. 3, when viewed from above, the wide section 30 b has a width Wb that increases toward the base end bracket 31. The width Wb of the wide section 30 b is not constant across the entire wide section 30 b and continues to increase from the predetermined position LP, at which the straight section 30 a and the wide section 30 b are smoothly continuous to each other, to the base end bracket 31. In this embodiment, the width Wb of the wide section 30 b has a maximum value of 570 mm. In this embodiment, a ratio of the width Wa of the straight section 30 a to the wide section 30 b is 15:19.

As illustrated in FIG. 3, when viewed from above, a first side surface S1 of the wide section 30 b is convexly curved toward the inner side of the body 30. Similarly, a second side surface S2 of the wide section 30 b is convexly curved toward the inner side of the body 30. The first side surface S1 is a part of a surface of the first side plate 35 and the second side surface S2 is a part of a surface of the second side plate 36.

In this embodiment, the wide section 30 b has a height that becomes smaller toward the base end bracket 31 from the straight section 30 a. On the other hand, as described above, the width of the wide section 30 b increase from the predetermined position LP, at which the straight section 30 a and the wide section 30 b are smoothly continuous to each other, to the base end bracket 31. With this configuration, the wide section 30 b, which is most likely subject to load, is able to have improved bending strength at the sides.

Configuration of Base End Bracket 31

FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 2. FIG. 5 is a partially expanded view of FIG. 4.

The base end bracket 31 is formed in a shape that is entirely tapered toward the body 30. The base end bracket 31 includes a first abutment surface S3, a second abutment surface S4, and a front end surface S5.

The first side plate 35 of the body 30 abuts against the first abutment surface S3. The first abutment surface S3 is formed so as to be angled with respect to the longitudinal direction of the body 30 such that the first abutment surface S3 follows the first side plate 35 that expands outward. The first abutment surface S3 is a part of a left side surface of the base end bracket 31.

The second side plate 36 of the body 30 abuts against the second abutment surface S4. The second abutment surface S4 is formed so as to be angled with respect to the longitudinal direction of the body 30 such that the second abutment surface S4 follows the second side plate 36 that expands outward. The second abutment surface S4 is a part of a right side surface of the base end bracket 31.

The front end surface S5 is continued to the first abutment surface S3 and the second abutment surface S4. In this embodiment, the front end surface S5 is formed into a flat plate, but the front end surface S5 is not limited to this shape.

Method of Manufacturing Boom 17

FIGS. 6A to 6E and FIG. 7 are schematic diagrams for showing a method of manufacturing the boom 17.

First, as illustrated in FIG. 6A, the bottom plate 34 having a rear end portion that flares toward the bottom is prepared.

Next, as illustrated in FIG. 6B, the first side plate 35 and the second side plate 36 are placed in parallel on the bottom plate 34 with a predetermined clearance therebetween.

Next, as illustrated in FIG. 6C, with the first side plate 35 and the second side plate 36 being fixed at the predetermined positions LP, rear end portions of the first side plate 35 and the second side plate 36 are pushed outward using a lining. More specifically, as illustrated in FIG. 7, with a pair of pressing tools 40 abutting against the predetermined positions LP on outer surfaces of the first side plate 35 and the second side plate 36, a lining tool 41 applies outward pressure to inner surfaces of the rear end portions of the first side plate 35 and the second side plate 36. At this time, the lining is adjusted to cause elastic deformation within a range that does not plastically deform the first side plate 35 and the second side plate 36.

Next, as illustrated in FIG. 6D, the base end bracket 31 is inserted between the respective rear end portions of the first side plate 35 and the second side plate 36 that have elastically deformed outward, and then the lining is removed, to thereby sandwich and fix the base end bracket 31 between the respective rear end portions of the first side plate 35 and the second side plate 36. Then, the bottom plate 34 and the first side plate 35 are welded together and the bottom plate 34 and the second side plate 36 are welded together. In addition, the base end bracket 31 is temporarily mounted to the first side plate 35 from the inner side, and the base end bracket 31 is temporarily mounted to and the second side plate 36 from the inner side.

Next, as illustrated in FIG. 6E, the top plate 33 is placed on top of the first side plate 35 and the second side plate 36. Then, the top plate 33 and the first side plate 35 are welded together and the top plate 33 and the second side plate 36 are welded together, to thereby fix the top plate 33.

The boom 17 includes the body 30 and the base end bracket 31. The body 30 includes the straight section 30 a and the wide section 30 b. When viewed from above, the width Wa of the straight section 30 a is substantially constant. When viewed from above, the width Wb of the wide section 30 b increases toward the base end bracket 31. The straight section 30 a and the wide section 30 b are smoothly continuous to each other.

As described above, because the wide section 30 b is configured to increase in the width Wb toward the base end bracket 31, the bending strength of the wide section 30 b at the sides can be improved. In addition, because the straight section 30 a and the wide section 30 b are smoothly continuous to each other, it is possible to reduce locally concentrating stresses in the body 30.

In the above-described embodiment, a case has been described in which a “box-shaped structure for a work machine” according to the present invention is applied to the boom 17, but the present invention is not limited thereto. The “box-shaped structure for a work machine” according to the present invention can also be applied to the arm 18. Even in this case, durability of the arm 18 can be improved with the body of the arm 18 having a width that increases toward the base end side bracket 18 b.

In the above-described embodiment, as illustrated in FIG. 6C, the first side plate 35 and the second side plate 36 are pushed outward using a lining, but the first side plate 35 and the second side plate 36 may be pushed outward by pushing the base end bracket 31 in between the first side plate 35 and the second side plate 36.

In the above-described example, the end boss EB that extends in the width direction is separately provided on the base end bracket 31, but the base end bracket 31 and the end boss EB may be formed integrally.

In the above-described example, an ingot formed by casting a metal material is used for the base end bracket 31, but the base end bracket 31 may be formed by forging or be formed of a metal plate. 

1. A box-shaped structure for a work machine, comprising: a body extending in a longitudinal direction; and a bracket connected to one end of the body, the body including a straight section and a wide section, the straight section having a substantially constant width when viewed from above, and the wide section being connected to the bracket and having a width that increases toward the bracket when viewed from above, and the straight section and the wide section being smoothly continuous to each other.
 2. The box-shaped structure for a work machine according to claim 1, wherein the body is formed of a top plate, a bottom plate, a first side plate and a second side plate; the bracket includes a first abutment surface that abuts against the first side plate and a second abutment surface that abuts against the second side plate; and each of the first abutment surface and the second abutment surface is angled with respect to the longitudinal direction of the body.
 3. The box-shaped structure for a work machine according to claim 1, wherein the body has a center boss centrally located in the longitudinal direction; the bracket has an end boss; the straight section is smoothly continuous to the wide section at a predetermined position between the center boss and the end boss; and a ratio of a first interval between a center axis of the center boss and the predetermined position to a second interval between a center axis of the end boss and the predetermined position is from 1:1 to 4:1.
 4. A method of manufacturing a box-shaped structure for a work machine, comprising: placing a first side plate and a second side plate on a bottom plate; pushing one end portion of the first side plate and one end portion of the second side plate outward using a lining; sandwiching and fixing a bracket between the one end portion of the first side plate and the one end portion of the second side plate; and fixing a top plate on top of the first side plate and the second side plate.
 5. The box-shaped structure for a work machine according to claim 2, wherein the body has a center boss centrally located in the longitudinal direction; the bracket has an end boss; the straight section is smoothly continuous to the wide section at a predetermined position between the center boss and the end boss; and a ratio of a first interval between a center axis of the center boss and the predetermined position to a second interval between a center axis of the end boss and the predetermined position is from 1:1 to 4:1. 